Alliance MLA for South Antrim John Blair said his thoughts were with the family and friends of those who were involved in the collision.
“There cannot possibly be worse news for any family coming up to the Christmas period,” he said.
“I know that Glenavy itself is a settled and close knit community and there will be much shock and sadness across that community also.”
In a separate incident on Saturday evening, emergency services were called to a two-vehicle collision near Lisburn.
Five people were taken to hospital – a man, two women and two children – after the incident on Saintfield Road at the junction of Old Ballynahinch Road.
Both women and a child are being treated for serious injuries.
